Reasoning system for reasoning with uncertainty
First Claim
1. A method, for practice on a computer, for reasoning with uncertainty in a rule-based reasoning system comprising a plurality of rules each having a premise and a conclusion to be determined true upon finding the premise to be true, said premise comprising at least one clause including a variable to which a value can be assigned, said method comprising the steps of:
- associating a value certainty interval with each value assigned to one of said rule premise variables, said value certainty interval having a lower and an upper bound respectively representative of amounts of confirmation and failure of refutation of the assigned value;
associating a sufficiency factor and a necessity factor with each said rule, said sufficiency factor representing a strength of belief that the rule conclusion is true given the rule premise is true, said necessity factor representing a strength of belief that the rule conclusion is false given the rule premise is false;
computing a premise certainty interval from the value certainty intervals respectively associated with the values assigned to the premise variables, a lower bound of said premise certainty interval being a first predetermined function of the respective value certainty interval lower bounds, an upper bound of said premise certainty interval being said first function of the respective value certainty interval upper bounds; and
firing one of said rules by computing a conclusion detachment certainty interval having a lower and an upper bound, said conclusion detachment interval lower bound being a second predetermined function of both said rule sufficiency factor and said premise certainty interval lower bound, the conclusion detachment upper bound being a third predetermined function of both said rule necessity factor and said premise certainty interval upper bound, said conclusion detachment interval lower and upper bounds respectively representing the amounts of confirmation and failure of refutation of the rule conclusion.
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Abstract
The invention is directed to an automated rule-based reasoning with uncertainty system and method for practicing same. The system has a three layer structure composed of representation, inference and control layers. Rule firings and conclusions are computed in the inference layer in a manner to propagate uncertainty information through the system in accordance with predetermined formulas designated by the control layer. Rule structures and conclusions and uncertainty information associated therewith are represented to the user in the representation layer.
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Citations
29 Claims
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1. A method, for practice on a computer, for reasoning with uncertainty in a rule-based reasoning system comprising a plurality of rules each having a premise and a conclusion to be determined true upon finding the premise to be true, said premise comprising at least one clause including a variable to which a value can be assigned, said method comprising the steps of:
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associating a value certainty interval with each value assigned to one of said rule premise variables, said value certainty interval having a lower and an upper bound respectively representative of amounts of confirmation and failure of refutation of the assigned value; associating a sufficiency factor and a necessity factor with each said rule, said sufficiency factor representing a strength of belief that the rule conclusion is true given the rule premise is true, said necessity factor representing a strength of belief that the rule conclusion is false given the rule premise is false; computing a premise certainty interval from the value certainty intervals respectively associated with the values assigned to the premise variables, a lower bound of said premise certainty interval being a first predetermined function of the respective value certainty interval lower bounds, an upper bound of said premise certainty interval being said first function of the respective value certainty interval upper bounds; and firing one of said rules by computing a conclusion detachment certainty interval having a lower and an upper bound, said conclusion detachment interval lower bound being a second predetermined function of both said rule sufficiency factor and said premise certainty interval lower bound, the conclusion detachment upper bound being a third predetermined function of both said rule necessity factor and said premise certainty interval upper bound, said conclusion detachment interval lower and upper bounds respectively representing the amounts of confirmation and failure of refutation of the rule conclusion. - View Dependent Claims (5, 6, 9)
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2. A method, for practice on a computer, for reasoning with uncertainty in a rule-based reasoning system comprising a plurality of rules each having a premise and a conclusion to be determined true upon finding the premise to be true, said premise comprising at least one clause including a variable to which a value can be assigned, said method comprising the steps of:
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associating a value certainty interval with each value assigned to one of said rule premise variables, said value certainty interval having a lower and an upper bound respectively representative of amounts of confirmation and failure of refutation of the assigned value; associating a sufficiency factor and a necessity factor with each said rule, said sufficiency factor representing a strength of belief that the rule conclusion is true given the rule premise is true, said necessity factor representing a strength of belief that the rule conclusion is false given the rule premise is false; computing a premise certainty interval from the value certainty intervals respectively associated with the values assigned to the premise variables, a lower bound of said premise certainty interval being a first predetermined function of the respective value certainty interval lower bounds, an upper bound of said premise certainty interval being said first function of the respective value certainty interval upper bounds; and firing one of said rules by computing a conclusion detachment certainty interval having a lower and an upper bound, said conclusion detachment interval lower bound being a second predetermined function of both said rule sufficiency factor and said premise certainty interval lower bound, the conclusion detachment upper bound being a third predetermined function of both said rule necessity factor and said premise certainty interval upper bound, said conclusion detachment interval lower and upper bounds respectively representing the amounts of confirmation and failure of refutation of the rule conclusion, wherein upon the same conclusion being provided by more than one rule in a predetermined group of said rules, said method comprises the additional step of; aggregating the same conclusions by computing a conclusion aggregation certainty interval having a lower bound that is a fourth predetermined function of the conclusion detachment interval lower bounds respectively computed for the rules reaching the same conclusion, an upper bound of said conclusion aggregation interval being said fourth predetermined function of the conclusion detachment interval upper bounds respectively computed for the rules reaching the same conclusion, said conclusion aggregation interval lower and upper bounds respectively representing the amounts of confirmation and failure of refutation of the aggregated conclusion. - View Dependent Claims (3, 4, 7, 8)
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10. A rule-based reasoning system for reasoning with uncertainty for practice on a computer, comprising:
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a knowledge base portion comprising a plurality of system rules each having a premise and a conclusion to be determined true upon finding the premise true, said premise comprising at least one clause including a variable to which a value can be assigned; a representation portion for representing to a system user a value certainty interval associated with each value assigned to one of said rule premise variables, said value certainty interval having a lower and an upper bound respectively representative of amounts of confirmation and failure of refutation of the assigned value; said representation portion additionally representing to the user a sufficiency factor and a necessity factor associated with each said rule, said sufficiency factor representing a strength of belief that said rule conclusion is true given said rule premise is true, said necessity factor representing a strength of belief that said rule conclusion is false given said rule premise is false; a control portion for selecting computational functions in accordance with which the value certainty interval associated with each said assigned value is propagated through said rule based system; an inference portion for computing a premise certainty interval from the value certainty intervals respectively associated with the values assigned to the premise clauses, a lower bound of said premise certainty interval being a first computational function of the respective value certainty interval lower bounds, said first function being selected in said control portion, an upper bound of said premise certainty interval being said first function of the respective value certainty interval upper bounds; and said inference portion firing each said rule by computing a conclusion detachment interval having a lower and an upper bound, the conclusion detachment interval lower bound being a second computational function of both said rule sufficiency factor and said premise certainty interval lower bound, the conclusion detachment interval upper bound being a third computational function of both said rule necessity factor and said premise certainty interval upper bound, said second and third functions being selected by said control portion, said conclusion detachment interval lower and upper bounds being respectively representative of the amounts of confirmation and failure of refutation of the rule conclusion. - View Dependent Claims (14, 15, 18, 19)
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11. A rule-based reasoning system for reasoning with uncertainty for practice on a computer, comprising:
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a knowledge base portion comprising a plurality of system rules each having a premise and a conclusion to be determined true upon finding the premise true, said premise comprising at least one clause including a variable to which a value can be assigned; a representation portion for representing to a system user a value certainty interval associated with each value assigned to one of said rule premise variables, said value certainty interval having a lower and an upper bound respectively representative of amounts of confirmation and failure of refutation of the assigned value; said representation portion additionally representing to the user a sufficiency factor and a necessity factor associated with each said rule, said sufficiency factor representing a strength of belief that said rule conclusion is true given said rule premise is true, said necessity factor representing a strength of belief that said rule conclusion is false given said rule premise is false; a control portion for selecting computational functions in accordance with the value certainty interval associated with each said assigned value is propagated through said rule based system; an inference portion for computing a premise certainty interval from the value certainty intervals respectively associated with the values assigned to the premise clauses, a lower bound of said premise certainty interval being a first computational function of the respective value certainty interval lower bounds, said first function being selected in said control portion, an upper bound of said premise certainty being said first function of the respective value certainty interval upper bounds; and said inference portion firing each said rule by computing a conclusion detachment interval having a lower and an upper bound, a conclusion detachment interval lower bound being a second computational function of both said rule sufficiency factor and said premise certainty interval lower bound, the conclusion detachment interval upper bound being a third computational function of both said rule necessity factor and said premise certainty interval upper bound, said second and third functions being selected by said control portion, said conclusion detachment interval lower and upper bounds being respectively representative of the amounts of confirmation and failure of refutation of the rule conclusion, and wherein said inference portion is adapted to compute a conclusion aggregation certainty interval for the same conclusion provided by more than one rule in a predetermined group of said rules, a lower bound of said conclusion aggregation interval being a fourth computational function of the conclusion detachment interval lower bounds respectively computed for the rules providing the same conclusion, an upper bound of said conclusion aggregation interval being said fourth function of the conclusion detachment interval upper bounds respectively computed for the rules providing the same conclusion, said fourth function being selected by said control portion, said conclusion aggregation interval lower and upper bounds being respectively representative of the amount of confirmation and failure of refutation of the aggregated conclusion. - View Dependent Claims (12, 13, 16, 17)
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20. A system, for practice on a computer, for reasoning with uncertainty in a rule-based reasoning system comprising a plurality of rules each having a premise and a conclusion to be determined true upon finding the premise to be true, said premise comprising at least one clause including a variable to which a value can be assigned, said reasoning system comprising:
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means for associating a value certainty interval with each value assigned to one of said rule premise variables, said value certainty interval having a lower and an upper bound respectively representative of amounts of confirmation and failure of refutation of the assigned value; means for associating a sufficiency factor and a necessity factor with each said rule, said sufficiency factor representing a strength of belief that the rule conclusion is true given the rule premise is true, said necessity factor representing a strength of belief that the rule conclusion is false given the rule premise is false; means for computing a premise certainty interval from the value certainty intervals respectively associated with the values assigned to the premise variables, a lower bound of said premise certainty interval being a first predetermined function of the respective value certainty interval lower bounds, an upper bound of said premise certainty interval being said first function of the respective value certainty interval upper bounds; and means for firing each of said rules by computing a conclusion detachment certainty interval having a lower and an upper bound, said conclusion detachment interval lower bound being a second predetermined function of both said rule sufficiency factor and said premise certainty interval lower bound, the conclusion detachment upper bound being a third predetermined function of both said rule necessity factor and said premise certainty interval upper bound, said conclusion detachment interval lower and upper bounds respectively representing the amounts of confirmation and failure of refutation of the rule conclusion. - View Dependent Claims (24, 26, 28, 29)
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21. A system, for practice on a computer, for reasoning with uncertainty system in a rule-based reasoning system comprising a plurality of rules each having a premise and a conclusion to be determined true upon finding a premise to be true, said premise comprising at least one clause including a variable to which a value can be assigned, said reasoning system comprising:
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means for associating a value certainty interval with each value assigned to one of said rule premise variables, said value certainty interval having a lower and an upper bound respectively representative of amounts of confirmation and failure of refutation of the assigned value; means for associating a sufficiency factor and a necessity factor with each said rule, said sufficiency factor representing a strength of belief that the rule conclusion is true given the rule premise is true, said necessity factor representing a strength of belief that the rule conclusion is false given the rule premise is false; means for computing a premise certainty interval from the value certainty intervals respectively associated with the values assigned to the premise variables, a lower bound of said premise certainty interval being a first predetermined function of the respective value certainty interval lower bounds, an upper bound of said premise certainty interval being said first function of the respective value certainty interval upper bounds; and means for firing each of said rules by computing a conclusion detachment certainty interval having a lower and upper bound, said conclusion detachment interval lower bound being a second predetermined function of both said rule sufficiency factor and said premise certainty interval lower bound, the conclusion detachment upper bound being a third predetermined function of both said rule necessity factor and said premise certainty interval upper bound, said conclusion detachment interval lower and upper bounds respectively representing the amounts of confirmation and failure of refutation of the rule conclusion, and wherein upon the same conclusion being provided by more than one rule in a predetermined group of said rules, said system additionally comprises; means for aggregating the same conclusions by computing a conclusion aggregation certainty interval having a lower bound that is a fourth predetermined function of the conclusion detachment interval lower bounds respectively computed for the rules reaching the same conclusion, an upper bound of said conclusion aggregation interval being said fourth predetermined function of the conclusion detachment interval upper bounds respectively computed for the rules reaching the same conclusion, said conclusion aggregation interval lower and upper bounds being respectively representative of the amount of confirmation and failure of refutation of the aggregated conclusion. - View Dependent Claims (22, 23, 27)
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25. [c,C] is said conclusion detachment interval;
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Ti is the T-norm function selected from said first function set; s is said rule sufficiency factor; n is said rule necessity factor; [b,B] is said premise certainty interval; and N is a negation operator such that N(α
)=1-α
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Specification